A birefringent lens grating is an essential element of a 2D/3D switching stereoscopic display. The birefringent lens grating generally comprises a lens array substrate and a liquid crystal material layer. The liquid crystal material layer is one kind of birefringent material. In particular, the liquid crystal material layer has a refractive index no to ordinary light and has a refractive index ne to extraordinary light. The lens array substrate preferably is one kind of monorefringent material having a refractive index np. In a manufacturing process of the birefringent lens grating, it is needed to ensure one of the refractive index ne and the refractive index no of the liquid crystal material layer to match with the refractive index np of the lens array substrate so that light having a first linear polarization direction may pass through an interface of the liquid crystal material layer and the lens array substrate without any deflection, and light having a second linear polarization direction different from the first linear polarization direction may undergo deflection when it passes through the interface of the liquid crystal material layer and the lens array substrate.
Therefore, how to determine a refractive index matching degree of the liquid crystal material layer and the lens array substrate is essential to the birefringent lens grating.